FAQ: Grooming for fish

In a freshwater tank, top up with conditioned tap water. In a marine tank, top up with fresh water, usually RO water, not salt water, because salt does not evaporate and its concentration would otherwise rise.

A lid or a glass cover helps most. Evaporation increases with high water and room temperature, strong aeration and air movement over the surface. A lid also stops fish jumping out.

Yes, but such water contains almost no minerals, so for freshwater tanks it is mixed with tap water or remineralised with special products. RO water is commonly used for shrimp, soft-water fish and marine tanks.

Well water can contain high nitrate, iron or other substances, and its make-up can change with the seasons. Before using it for an aquarium, test it with kits or in a lab and watch how the fish react to the first changes.

Rainwater can be contaminated with dirt from roofs and gutters, air pollutants or metals, so it is risky. Some experienced aquarists use it, but only when collected cleanly and tested. Tap water is safer for beginners.

A tank without a filter struggles to keep water clean, so it does not suit most fish. If one is used anyway, the water must be changed much more often and very few animals kept. Fitting a small, quiet filter is usually easier.

A betta needs a heated tank with gentle filter flow. In such a tank part of the water is commonly changed every week, and the smaller the tank, the more often it needs changing, because waste builds up faster.

Usually not. A small round bowl has little surface area, is hard to fit with a filter and heater, and its water conditions change very quickly. Even small fish do better in a rectangular tank with a filter.

Handy for a nano tank are a small siphon with thin tubing, a mini glass scraper or magnet, a fine net and long tweezers. A large syringe or pipette helps for changing small amounts of water and sucking up debris.

Shrimp are sensitive to sudden changes, so change smaller amounts of water and add new water slowly at the same temperature and parameters. Put mesh over the siphon and cover the filter intake with a sponge.

Some can be, especially those containing copper, some algae and snail treatments, and medications. Before using any product in a tank with shrimp, read the label to see whether it is safe for invertebrates.

Goldfish eat a lot and produce a lot of waste, so they need a roomy tank, a strong filter and frequent water changes. They dig in the substrate, so siphon it regularly and choose sturdy plants.

Digging fish constantly reshape the bottom and stir up dirt, so the filter needs to be strong enough and its sponges cleaned more often. Place rocks directly on the tank bottom rather than on the gravel so they cannot topple when the fish dig.

Ponds are usually cleaned in spring and autumn: scoop out leaves and sludge, trim the plants and clean the filter. There is no need to drain all the water, which upsets the balance. A pond vacuum is handy for bottom sludge.

In autumn stretch a net over the pond against leaves, remove dead plants and sludge, and gradually reduce feeding as it cools. The pond must be deep enough, and in winter an ice-free spot should remain so gases can escape.

People use floating ice preventers, pond heaters or an air pump whose bubbles keep a spot open. Do not smash the ice, because the shock waves stress the fish. Ice can be carefully melted with warm water instead.

Rinse pond filter sponges in pond water, not tap water, so the beneficial bacteria survive. Clean the filter when the flow drops, and in spring start it early so the bacteria recover before the fish start feeding actively.

In spring there is more sunshine and nutrients have built up while plants are not yet growing, so floating algae bloom. Water plants, partial shade, moderate feeding and a UV steriliser help. The water usually clears once the plants grow.

In cold water fish metabolism is slow and they barely digest food. Feeding starts once the water warms steadily, often around 10 °C, with small amounts of easily digested food. A thermometer makes it easy to track the water temperature.

String algae can be pulled out with a rake, a special brush or a stick twirled to wind them up. More plants, shade and fewer nutrients help reduce them. Leave the removed algae at the edge for a while so small creatures can crawl back into the water.